CSLB C-36 Plumbing ContractorRough-in PlumbingHard
A plumbing inspector is reviewing the rough-in for a new residential DWV system. The inspector notes that a horizontal wet vent serves a lavatory and a shower. What is the maximum developed length permitted for the wet vent from the furthest fixture trap weir to the vent stack or stack vent?
- A12 feet
- B8 feet
- C6 feet
- D10 feet
Show answer & explanationAnswer & explanation
Correct answer: C. 6 feet
The California Plumbing Code (CPC) limits the developed length of horizontal wet vents to prevent excessive pressure fluctuations and ensure proper venting. For a 2-inch wet vent (typical for lavatory and shower), the maximum developed length is 6 feet from the furthest trap weir to the connection to a vent stack or stack vent.
Why the other options are wrong
- A. 12 feet is incorrect and far exceeds the code limit for a horizontal wet vent.
- B. 8 feet is incorrect and exceeds the code limit for this scenario.
- D. 10 feet is incorrect and significantly exceeds the code limit.
Horizontal Wet Vent Length
The maximum permissible developed length of a horizontal wet vent pipe from the furthest fixture trap weir to its connection to a dry vent or stack vent.
- Prevents trap siphonage or backpressure.
- Length limits vary by pipe size and fixture units.
- Ensures adequate air circulation in the DWV system.
Memory trick: Wet Vents are Short: 'Six' feet is the 'Secret' for Small Fixtures.